1. Field of the Invention
The present invention generally relates to an apparatus for supplying gamma signals, and more particularly, to an apparatus for supplying gamma signals in a Thin-Film-Transistor-Liquid-Crystal-Display (TFT-LCD).
2. Description of the Related Art
Semiconductor integrated circuit products and various appliances often have high-functionality and high-density. Therefore, the assembly package technique normally also requires high functionality and high density. Accordingly, it may be desirable to generally improve surface mount techniques.
In a Thin-Film-Transistor (TFT) panel, a surface mount technique may need a conversion from a Tape Automated Bonding (TAB) scheme into a Chip On Glass (COG) scheme. If this is possible, cost saving during the manufacturing process may be achieved.
The TAB scheme normally involves connecting chips to external leads or Printed Circuit Board (PCB) circuits using tapes. Using tapes eliminates the need to wire use. The COG scheme normally requires attaching bare chips directly to a glass substrate.
When compared to an individual package, the COG scheme has the advantages of high-density, high-functionality, low cost, high-productivity, etc. Also, this method has improved capacitance and conductance. Another advantage when compared to a mold package is that signal transmission distances can be significantly shortened due to the substantial exclusion of lead frames.
However, the COG scheme has a disadvantage in that all signals required by a conventional LCD driver IC (LDI) chip may not be fully accommodated. In particular, due to spatial limitation of a substrate, all the needed signal lines may not be accommodated.
At least one signal used by an LDI chip may include a gamma correction signal. The gamma signal may define the brightness and contrast of a display. A correction of the gamma signal may be required to reduce the blooming or blurring of a display and thereby maintain constant brightness of substantially the whole display.
FIG. 1 is a view showing the structure of a conventional apparatus for supplying gamma signals in a TFT panel. As shown in FIG. 1, a conventional gamma signal supplying unit may include a gamma signal generator 10 and a gray level resistor array 11. The gamma signal generator 10 may output voltages, VR1 through VR8 for each resistor, in parallel. The gray level resistor array 11 subdivides the voltage values output in parallel, respectively, and outputs one level value among all 256 levels of brightness values.
However, when using a surface mount technique of the COG scheme, parallel transmission of voltages may be required an increase in the number of signal lines. But as discussed, the surface mount technique of the COG scheme has limited signal line availability. Accordingly, it may be necessary to reduce the number of signal lines for providing gamma signals.
An exemplary embodiment of the present invention may provide a gamma signal supplying apparatus capable of reducing the number of signals to be transmitted. This may be achieved by transmitting as a serial signal a gamma signal among the signals required by an LDC driver IC (LDI) chip.
According to one exemplary embodiment of the present invention, a gamma signal supplying apparatus may include a timing controller for storing predetermined gamma values as digital values, and for transmitting one of the digital values serially. The gamma supplying apparatus may further include a gamma digital-to-analog controller (DAC) for receiving the serial digital gamma value, and for converting the serial digital gamma value into a first analog gamma value, and a plurality of column drive units, each of the plurality of column drive units for generating a second analog gamma value, for comparing the second analog gamma value to the first analog gamma value, and for outputting a gray level value based on the second analog gamma value if both values are substantially identical.
According to one exemplary embodiment of the present invention, a gamma signal supplying apparatus may include a timing controller for storing a predetermined gamma values as digital values, for transmitting one of the digital gamma values serially, and for outputting a reference digital code, a gamma digital-to-analog converter (DAC) for receiving the serial digital gamma value, for converting the digital gamma value into a first analog gamma value, for comparing the first analog gamma value to a second analog gamma value input from a following unit, and for outputting the comparison result to the timing controller, and a plurality of column drive units, each the plurality of column drive units for receiving the reference digital code, for generating a second analog gamma value corresponding to the reference digital code to output the same to the gamma DAC, for receiving a predetermined indication signal from the timing controller, and for outputting a gray level value based on the second analog gamma value, wherein the timing controller receives the comparison result, and outputs the indication signal to the corresponding column drive unit if the first and second analog the gamma values are substantially identical.
According to yet another exemplary embodiment of the present invention, a gamma signal supplying apparatus may include a timing controller for storing predetermined gamma values as digital values, for transmitting one among the stored digital values serially, and for outputting a first reference digital code and a second reference digital code, a first column drive unit for generating a first analog gamma value corresponding to the first reference digital code, for outputting a gray level value based on the analog gamma value, the first column drive unit including a first comparator for comparing the first analog gamma value with a second analog gamma value input from a following unit, and for outputting the compared result to the timing controller, and a plurality of second column drive units, each of the second column drive units serially connected and positioned behind the first column drive unit, for generating a second analog gamma value corresponding to the second reference digital code to output the same to a previous column drive unit, for outputting a gray level value based on the second analog gamma value if a predetermined indication signal is received from the timing controller. The second column drive unit includes a second comparator for comparing the second analog gamma value with a third analog gamma value inputted from a following unit, and for outputting the compared result to the timing controller, wherein the timing controller outputs the indication signal to one of two column drive units and comparison targets if values compared by the first or second comparator are substantially identical.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.